Regulatory and siting restrictions are such that many solid waste operators prefer to expand their existing landfill footprint as much as possible instead of finding a new disposal footprint at a different location. As landfills are getting larger in height and greater in footprint area, the location of leachate tanks, leachate ponds, or discharge points to an on-site or off-site leachate treatment plant usually does not change. A larger footprint means leachate force mains are getting longer forcing the existing pumps to work harder to push leachate through the system to a target point. Some operators carry on with the same pumps for decades and do not monitor the performance of the pumps after expanding the landfill footprint, which could be more costly in the long-term.
Hydraulic Evaluations for Lateral Expansion
The longer leachate force main with possibly additional bends in the line increases friction in the line and causes flow rates to reduce to unexpected levels. We recommended that landfill operators evaluate the performance of the existing pumps along with new pumps when designing a lateral expansion. Such an evaluation may require hydraulic analysis of the entire network of pipes along with pumps, or only the segment of the network affected by the expansion. However, the effort is minimal in comparison to the operating costs of inefficient flow and overtaxing the equipment.
Sometimes the results of a hydraulic evaluation may require up-sizing all or specific pumps in leachate sumps because not enough flow can go through the force main due to high friction loss in the expanded leachate force main. Up-sizing pumps may be achievable depending on the type of the leachate sump, i.e., riser system or vertical manholes. If the up-sized pump in a riser system is too long to fit inside a riser system, or so long that it makes routine maintenance too cumbersome, your engineer may consider enhancing the functionality of the design.
Inline and Offline Pumps
Booster pumps located along an expanded leachate force main can certainly be an option. Booster pumps can be the inline or offline type. Install the inline pumps on the actual force main, and position the offline type on the side so that liquids go through bends and elbows to reach the pump, and again through bends and elbows to get back in the force main. In either case, the booster pump adds hydraulic energy to the flow inside the force main to push the liquids at a compensated pressure through the remainder of the force main and to the target point.
Operators need to be aware of the dynamic nature of the leachate piping network and the role of booster pumps in the dynamic environment. Changes to the flow in the force main may change following a landfill expansion when the new cells are coming online increasing leachate generation. Alternatively, after closing portions of the landfill slopes, that decreases leachate generation over time. Sometimes booster pumps have to be up-sized or downsized depending on the flow and pressure in the system.
Optimizing Performance, Reduce O&M Costs
The cost of replacing pumps, up-sizing, or downsizing, is insignificant compared to the revenue that landfills generate. Proper adjustment of the pumping system keeps the entire network operating at the appropriate range of pressure, and velocity in the line; increasing the life of the pumping system. Less wear and tear on the system produces a reduction in maintenance costs along with less equipment downtime.
Lower maintenance requirements may also reduce the number of personnel required to keep the system in operational condition. Landfills with a large pumping system employing a second technician because of the high maintenance of multiple pumps may find a single technician sufficient for the upkeep of the system. Proper sizing of pumps and operating the pumping system as designed within the evaluation parameters can significantly reduce the cost and frequency of pump maintenance.
About the Author: Ali Khatami, PhD, PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Landfill Design and Construction Quality Assurance. He has nearly 40 years of research and professional experience in mechanical, structural, and civil engineering.
Landfill Engineering and Leachate Management
At EUEC 2019 learn how SCS can minimize leachate and contact water management at coal combustion residual (CCR) landfills using good design, physical controls, and operational practices.
Through this SCS presentation of case studies, you will learn how to assess leachate and contact water management issues and implement techniques to minimize leachate and contact water management at your landfill.
Leachate management and contact water management at CCR landfills can be expensive, cause operational headaches, and divert valuable resources from other critical plant needs. Our presentation will provide you with useful tools to ensure your landfill is designed and operated to effectively reduce leachate and contact water and alleviate operator stress. We will present case studies that highlight how design features, physical controls, and operational practices have effectively decreased leachate and contact water management at CCR landfills.
2019 EUEC in San Diego, February 25-17, 2019. Conference details here.
Learn how to minimize leachate and contact water management at coal combustion residual (CCR) landfills using good design, physical controls, and operational practices.
Through this SCS presentation of case studies, you will learn how to assess leachate and contact water management issues and implement techniques to minimize leachate and contact water management at your landfill.
Leachate management and contact water management at CCR landfills can be expensive, cause operational headaches, and divert valuable resources from other critical plant needs. Our presentation will provide you with useful tools to ensure your landfill is designed and operated to effectively reduce leachate and contact water and alleviate operator stress. We will present case studies that highlight how design features, physical controls, and operational practices have effectively decreased leachate and contact water management at CCR landfills.
2019 EUEC in San Diego, February 25-17, 2019. Conference details here.
Learn how to minimize leachate and contact water management costs at coal combustion residual (CCR) landfills using good design, physical controls, and operational practices. Through the SCS use of case studies, you will learn how to assess leachate and contact water management issues and implement cost-saving techniques at your landfill.
Leachate management and contact water management at CCR landfills can be expensive, cause operational headaches, and divert valuable resources from other critical plant needs. The SCS presentation at USWAG will provide you with useful tools to ensure your landfill is designed and operated to cost-effectively reduce leachate and contact water and alleviate operator stress. We will present case studies that highlight how design features, physical controls, and operational practices have effectively decreased leachate and contact water management at CCR landfills.
SCS Engineers – Serving Utilities Nationwide
Article and Slideshow of Landfills using these Best Practices to prevent leachate. Click Hot off the Press to view.
Landfill operators are seeking new means to dispose of leachate generated at their facilities more economically. Rising costs of leachate treatment at publicly owned treatment works (POTWs) obliges landfill operators to look for alternative disposal means at a lower price. These situations encourage landfill operators and consultants to do more with less when designing preventative solutions to reduce leachate generation in the first place.
Upstream measures to reduce leachate generation range from standard operating procedures to innovative ideas with significantly high benefit to cost ratios. SCS compiled a list of our Top 10 measures to consider, including:
1. Grading – Creating landfill plateaus to maximize rainwater runoff toward perimeter storm water ditches, using low permeable soil to seal landfill slopes that will not receive waste for an extended time.
2. Caps & Covers – Using temporary geomembrane caps over areas that will not receive waste for a long time. Constructing final cover over landfill final slopes to eliminate rainwater percolation into landfill.
3. Swales – Constructing temporary and strategic swales on landfill outside slopes to capture rainwater runoff before causing soil erosion on the slope and to convey runoff water to perimeter ditches.
4. Berms & Downchutes – Constructing temporary berms and swales on landfill slopes that drain toward new disposal cells to capture water before reaching waste in the new cell and directing water to perimeter ditches. Also, constructing a berm at the crest of slopes to minimize the flow of rainwater runoff over slopes that are causing soil erosion. Constructing engineered temporary and sturdy downchutes for rainwater runoff from top areas of the landfill to the perimeter ditches.
5. Tarps – Installing rain tarp over a portion of a new cell that will not be in service for some time.
6. Exposure – Minimizing exposure of the active face while the remaining areas are properly graded to shed rainwater runoff to perimeter ditches.
7. Shedding – Grading the top area of each lift to shed rainwater runoff to outside slopes and the perimeter ditches.
8. Plantings – Installing sod or seeding on exterior slopes and those interior slopes that will not receive waste for an extended time to reduce soil erosion.
9. Roads – Constructing ditches adjacent to access roads to safely convey runoff water to the bottom of the slope – pitching access roads toward the ditch adjacent to the road, and building a proper road surface to minimize erosion during severe storms while lasting long under traffic loading.
10. Maintenance – Establishing routine maintenance protocol for the aforementioned measures because regular maintenance sustains long life and performance.
For facilities outside the landfill area, special measures, such as using floating covers on leachate ponds or canopies over operations that could potentially generate leachate without the canopy, also help reduce leachate generation.
Upstream measures are not necessarily limited to our Top 10 list but depend on the type and extent of operations at a facility. The will of the landfill operator and the expertise of the solid waste engineer can go a long way to reducing leachate generation at landfill facilities, and we all strive for that.
More about Liquids Management including case studies.
Many landfill operators and owners are now spending more than 10 or 20 cents per gallon for leachate management, which can become quite costly. One of the primary reasons that leachate management has become an expensive challenge in the United States is more stringent regulatory policies regarding the discharge of liquids into public waters. The regulations affect publicly owned treatment works (POTW), which has led some POTWs to require that leachate entering their plants have adequate pre-treatment to remove contaminants. Under these circumstances, some landfills are forced to collect and haul their leachate to a different POTW or to consider installation of pre-treatment equipment themselves.
Each landfill needs a solution to its leachate management issues that depends on applicable regulatory restrictions, the capability of the local POTW, and the leachate composition. Due to chemical reactions and biological activity inside the landfill, the leachate’s temperature is frequently warmer than area groundwater. Also, leachate is odorous, and generally brown in color, with colloidal suspended solids. The composition of leachates depends on the composition of a landfill’s waste, the landfill’s decomposition stage, and weather conditions. Many factors are evaluated to arrive at an efficient and economical treatment method for disposal of landfill leachate.
There are some treatment alternatives available to reduce the high organic and nitrogen loads in leachate. For some leachate applications, the treatment methods are sufficient to allow the POTW to process the leachate safely. If treatment is not possible, or cost prohibitive another alternative is to pre-treat the leachate, lowering the contaminant load to prevent subsurface precipitation, and then dispose of it using deep well injection. Some states require little or no pre-treatment before discharging leachate to deep injection wells.
The following technologies are available for the pre-treatment of landfill leachate: biological processes for wastewater treatment such as membrane bioreactors, sequencing batch reactors, activated sludge processes plus reverse osmosis. Wet oxidation processes, activated carbon adsorption, as well as precipitation, coagulation, and flocculation techniques are also used, depending on the contaminants and their concentrations. These two counties are using a combination of treatment technologies for their leachate management strategies.
Hillsborough County’s 60,000 Gallon Per Day Leachate Treatment Facility at Southeast County Landfill
New Hanover County’s Landfill Leachate Treatment Plant Using Reverse Osmosis
Effective leachate management applies unique combinations of technologies which most adequately address the previously mentioned factors. To provide a truly sustainable solution to leachate management, SCS suggests another approach, which is to consider the landfill design and operations as part of the solution. By using the existing landfill design and operations, SCS develops an integrated approach to leachate management that is preventative. The benefits of using an integrated approach are that they are often a more cost-effective solution in the long-term, sustainable, working with the existing landfill’s infrastructure.
Waste Management is using an integrated approach at Monarch Hill Landfill in Pompano Beach, Florida. Monarch Hill Landfill is a 385-acre landfill with a waste flow of 5,000 tons per day. SCS helped decrease leachate formation as part of overall landfill design and operation. Waste Management reduced leachate formation using the following methods:
Temporary caps – SCS designed and provided monitoring services during installation of a 10-acre temporary geomembrane cap over a portion of the top intermediate plateau of the landfill. It reduced leachate generation, decreased odors, increased gas collection efficiencies, and addressed leachate seeps on the slope, as well as making surface water runoff over the top of the landfill easier and more efficient.
Final covers – SCS designed, permitted, and provided monitoring services during construction of six partial closure projects. The final covers were equipped with leachate toe drain systems below the final cover geomembrane, enabling leachate seeps to be collected and disposed of efficiently. The design also allowed collection of gas from the lower portion of the slope after completion.
Rainwater Toe Drain Systems – SCS designed a toe drain system above the final cover geomembrane that enabled water to be collected and diverted to the landfill perimeter ditches, preventing pore pressure build up and keeping the system stable.
Tack-on Swales – SCS designed tack-on swales that were implemented to catch runoff and convey water to downchute pipes. The swales could be easily adjusted based on the size of each partial closure and the overall management of stormwater.
Our approach is to develop a robust, tailored liquids management program comprised of the most appropriate technologies and engineering design to tackle the unique set of challenges facing each landfill client. In an era of doing more with less, clients find our programs are more cost-effective because they are more efficient and well designed.
Learn more at SCS Liquids Management
Contact one of our National Experts or :
Darrin Dillah: Landfill Leachate – Upstream
Ron Wilks: Landfill Leachate – Downstream and Evaporators
Monte Markley: Deep Well Injection
Bob Speed: Dewatering
Ali Khatami: Landfill Engineering and Construction Impacts on Liquids Managment
Sam Cooke: Industrial Wastewater Treatment
A variety of CCB/CCP related topics guaranteed to enhance your knowledge. Click the title to read or share these papers.
Jeff Marshall – Mitigating Hydrogen Sulfide Issues at Coal Combustion Residuals and Municipal Solid Waste Co-disposal Sites – Learn about the biological, chemical and physical conditions necessary for FGD decomposition and hydrogen sulfide generation. Marshall will explore technologies that remove and treat hydrogen sulfide from landfill gas and present recommendations for reducing the potential for FGD decomposition at co-disposal facilities.
Eric Nelson and Lindsay Motl – Working Through Location Restrictions to Expand the Ottumwa Midland Landfill – The final Coal Combustion Residual (CCR) rule introduces new challenges for companies developing new landfills or expanding existing sites. Join us to learn how Alliant Energy overcame these challenges and expanded the Ottumwa Midland Landfill (OML) to accommodate increased byproduct disposal rates from new emission control projects.
Steve Lamb and Floyd Cotter – Selecting the Right Closure Cap Option for Your Surface Impoundment or CCR Landfill – Alternative capping options have recently emerged in the industry, such as exposed geomembrane liners or synthetic turf/geomembrane liner systems. Some of these alternative capping options have many advantages over their traditional counterparts. These experts describe the advantages and disadvantages of alternative capping options.
Thanks to you, our clients, SCS Engineers has received many awards and industry recognitions for research achievements and technology innovations. Engineering News-Record (ENR) recently released the Top 500 Design List, ranking SCS Engineers in the top 100 for the 9th year in a row. In the same publication, SCS is ranked in the Top 10 Sewerage/ Wastewater Firms.
Thank you for your friendship, your business, and the opportunity to serve you.
Jeff Marshall, PE, SCS Engineers will be presenting the topic of Hydrogen Sulfide Issues at CCR and MSW Co-Disposal Sites during the EREF and NWRA sponsored Coal Ash Management Forum in July.
The co-disposal of municipal solid waste and coal combustion residuals – particularly flue gas desulfurization (FGD) material – poses a significant concern regarding the generation of hydrogen sulfide gas. Hydrogen sulfide has an exceptionally low odor threshold, and can pose serious health concerns at higher concentrations. This presentation will identify the biological, chemical and physical conditions necessary for FGD decomposition and hydrogen sulfide generation. Recommendations for reducing the potential for FGD decomposition at co-disposal facilities will be presented. Technologies for the removal and treatment of hydrogen sulfide from landfill gas will also be addressed.
Jeff Marshall, PE, is a Vice President of SCS Engineers and the Practice Leader for Environmental Services in the Mid-Atlantic region. He also serves as the SCS National Expert for Innovative Technologies. He has a diversified background in environmental engineering and management, with emphasis on the chemical and human health aspects of hazardous materials and wastes. Mr. Marshall’s experience with hydrogen sulfide, odors, sulfate decomposition in landfills, and ash issues includes scores of projects dating back to the 1980s.
SCS Coal Combustion Residual Services
